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    <script>
        let num1 = 1;
        console.log(typeof num1); // 变量num1的类型
        let num2 = 2.1;
        console.log(typeof num2);
        console.log(num2 + 0.2); // 不擅长精度计算

        let str = '张';
        let str2 = '斯发';
        console.log(str + str2);
        console.log(`${str}${str2}`);  

        let a ;
        console.log(typeof a);
        a = 1;
        console.log(typeof a);

        let b = null; // 已经知道未来的数据类型
        let c = undefined; // 不知道未来的数据类型值的类型

        let d = true;


        let mm = {
            name: '陈',
            hometown: '望仙',
        }
        console.log(mm);
        console.log(typeof mm)
    </script>
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